Effect Of UV Treatment Research Articles

Influence of UV-B and culinary treatment on vitamin D2 and agaritine in button mushrooms

This study investigated the effects of different culinary treatments on the levels of vitamin D2 and agaritine in irradiated white button mushrooms. In addition, the intake of this vitamin via mushroom dishes was evaluated. In fresh irradiated white button mushrooms, the vitamin D2 content was 21.5 ± 2.4 µg/100 g fresh weight, 42 % of which was in the cap skin. The highest losses of vitamin D2 (63 %) were found in samples boiled in acidic water. In contrast, the lowest losses were found in samples boiled in non-acidified water. In the baking and frying experiments, vitamin D2 retention depended more on the cooking time than on the temperature. This resulted in high-heat frying being the second-best treatment for retaining vitamin D2 content in the samples. In the case of agaritine, no effect of UV treatment on its content was observed, and cooking treatment reduced its consumption. At the same time, the formation of toxic degradation products was not observed. The Recommended Daily Intake (RDI) of vitamin D can be achieved by consuming about 75–190 g of cooked, irradiated white button mushrooms, which can thus be an important dietary source of this vitamin.

Effect of secondary and tertiary wastewater treatment methods on opioids and the subsequent environmental impact of effluent and biosolids

Opioids are widely distributed, potent prescription analgesics that are known to be diverted for illicit use. Their prevalence of use is reflected by high concentrations of parent compounds and/or metabolites found in samples collected from wastewater treatment plants. Given that treatment byproducts enter the environment through several routes, the consequences of insufficient removal by treatment methods include unwanted environmental exposure and potential to disrupt ecosystems. Activated sludge treatment has been widely investigated for a large suite of prescription opioids but the same cannot be said for UV and chlorination. Additionally, the biosolid cycle of opioids has been overlooked previously. This study aimed to determine the extent to which secondary and tertiary wastewater treatment methods remove opioids from influent, and the associated environmental exposure for those persistent, as well as the fate of opioids in biosolids. Membrane bioreactor treatment proved effective for natural and semi-synthetic opioids while the effect of UV treatment was negligible. Chlorination was the most effective treatment method resulting in effluent with concentrations below theoretical predicted no-effect concentration. Biosolids are not subjected to any additional biological or chemical treatment after membrane bioreactor treatment and the levels detected in biosolid used as fertiliser had several opioids at potentially hazardous concentrations, indicated by a QSAR theoretical model. This data indicates a potential issue regarding the treatment process of biosolids and reliance on chlorination for effluent treatment that should be investigated in other treatment plants.

Effect of UV Irradiation on the Structural Variation of Metal Oxide-Silica Nanocomposites for Enhanced Removal of Erythromycin at Neutral pH

In this study, the effect of UV treatment on the physicochemical properties and structural variation of metal oxide-silica nanocomposites (Mn2O3-Fe2O3@SiO2) has been investigated. Based on the results, UV irradiation significantly affects the nanocomposite structure, where SiO2 network reconfiguration, change in surface OH group density, and surface area were observed. Erythromycin (ERY) has been chosen as a module pollutant to compare the performance of the pristine and UV-treated nanocomposites. The pristine nanocomposite had a high adsorption efficiency (99.47%) and photocatalytic activity (99.57%) at neutral pH for ERY in the first cycle, and this efficiency decreased significantly for the multiple cycles. However, different results have been observed for the UV-treated nanocomposite, where it retained its performance for ten consecutive cycles. This enhanced performance is attributed to the structural modifications after UV exposure, where increased surface area, pore volume, and OH group density resulted in an increased number of the possible mechanisms responsible for the adsorption/oxidation of ERY. Moreover, oxidation of adsorbed molecules by UV light after each cycle can also be another reason for enhanced removal. For the first time, the fate of ERY is studied using regenerated nanocomposites after the last cycle. LC/MS/MS results showed that ERY degraded in 20 min, and the produced reaction by-products were adsorbed by nanocomposites. This study could be a foundation research for the practical approaches for the regeneration of nanomaterials and the successful removal of organic pollutants from aquatic environments.

Effects of UV Treatment on Ceria-Stabilized Zirconia/Alumina Nanocomposite (NANOZR).

Nanostructured zirconia/alumina composite (NANOZR) has been explored as a suitable material for fabricating implants for patients with metal allergy. In this study, we examined the effect of UV treatment on the NANOZR surface. The experimental group was UV-treated NANOZR and the control group was untreated NANOZR. Observation of the surface of the UV-treated materials revealed no mechanical or structural change; however, the carbon content on the material surface was reduced, and the material surface displayed superhydrophilicity. Further, the effects of the UV-induced superhydrophilic properties of NANOZR plates on the adhesion behavior of various cells were investigated. Treatment of the NANOZR surface was found to facilitate protein adsorption onto it. An in vitro evaluation using rat bone marrow cells, human vascular endothelial cells, and rat periodontal ligament cells revealed high levels of adhesion in the experimental group. In addition, it was clarified that the NANOZR surface forms active oxygen and suppresses the generation of oxidative stress. Overall, the study results suggested that UV-treated NANOZR is useful as a new ceramic implant material.

Tuning of Titanium Microfiber Scaffold with UV-Photofunctionalization for Enhanced Osteoblast Affinity and Function.

Titanium (Ti) is an osteoconductive material that is routinely used as a bulk implant to fix and restore bones and teeth. This study explored the effective use of Ti as a bone engineering scaffold. Challenges to overcome were: (1) difficult liquid/cell infiltration into Ti microfiber scaffolds due to the hydrophobic nature of Ti; and (2) difficult cell attachment on thin and curved Ti microfibers. A recent discovery of UV-photofunctionalization of Ti prompted us to examine its effect on Ti microfiber scaffolds. Scaffolds in disk form were made by weaving grade 4 pure Ti microfibers (125 µm diameter) and half of them were acid-etched to roughen the surface. Some of the scaffolds with original or acid-etched surfaces were further treated by UV light before cell culture. Ti microfiber scaffolds, regardless of the surface type, were hydrophobic and did not allow glycerol/water liquid to infiltrate, whereas, after UV treatment, the scaffolds became hydrophilic and immediately absorbed the liquid. Osteogenic cells from two different origins, derived from the femoral and mandibular bone marrow of rats, were cultured on the scaffolds. The number of cells attached to scaffolds during the early stage of culture within 24 h was 3–10 times greater when the scaffolds were treated with UV. The development of cytoplasmic projections and cytoskeletal, as well as the expression of focal adhesion protein, were exclusively observed on UV-treated scaffolds. Osteoblastic functional phenotypes, such as alkaline phosphatase activity and calcium mineralization, were 2–15 times greater on UV-treated scaffolds, with more pronounced enhancement on acid-etched scaffolds compared to that on the original scaffolds. These effects of UV treatment were associated with a significant reduction in atomic carbon on the Ti microfiber surfaces. In conclusion, UV treatment of Ti microfiber scaffolds tunes their physicochemical properties and effectively enhances the attachment and function of osteoblasts, proposing a new strategy for bone engineering.

The impact of UV treatment on microbial control and DBPs formation in full-scale drinking water systems in northern China

To manage potential microbial risks and meet increasingly strict drinking water health standards, UV treatment has attracted increasing attention for use in drinking water systems in China. However, the effects of UV treatment on microbial control and disinfection by-products (DBPs) formation in real municipal drinking water systems are poorly understood. Here, we collected water samples from three real drinking water systems in Beijing and Tianjin to investigate the impacts of UV treatment on microbial control and DBP formation. We employed heterotrophic plate count (HPC), flow cytometry (FCM), quantitative PCR analysis, and high-throughput sequencing to measure microorganisms in the samples. Different trends were observed between HPC and total cell count (measured by FCM), indicating that a single indicator could not reflect the real degree of biological re-growth in drinking water distribution systems (DWDSs). A significant increase in the 16S rRNA gene concentration was observed when the UV system was stopped. Besides, the bacterial community composition was similar at the phylum level but differed markedly at the genera level among the three DWDSs. Some chlorine-resistant bacteria, including potential pathogens (e.g., Acinetobacter) showed a high relative abundance when the UV system was turned off. It can be concluded that UV treatment can mitigate microbial re-growth to some extent. Finally, UV treatment had a limited influence on the formation of DBPs, including trihalomethanes, haloacetic acids, and nitrogenated DBPs. The findings of this study may help to understand the performance of UV treatment in real drinking water systems.

Organic Matter Controls of Iron Incorporation in Growing Sea Ice

This study presents the first laboratory-controlled sea-ice growth experiment conducted under trace metal clean conditions. The role played by organic matter, in the incorporation of iron (Fe) into sea ice was investigated by means of laboratory ice-growth experiments using a titanium cold-finger apparatus. Experiments were also conducted to understand the role of extracellular polymeric substances (EPS) in the enrichment of ammonium in sea ice. Sea ice was grown from several seawater solutions containing different quantities and qualities of particulate Fe (PFe), dissolved Fe (DFe) and organic matter. Sea ice and seawater were analyzed for particulate organic carbon and nitrogen, macro-nutrients, extracellular EPS, PFe and DFe, and particulate aluminium. The experiments showed that biogenic PFe is preferentially incorporated into sea ice compared to lithogenic PFe. Furthermore, sea ice grown from ultra-violet (UV) and non-UV treated seawaters exhibits contrasting incorporation rates of organic matter and Fe. Whereas the effects of UV-treatments were not always significant, we do find indications that the type or organic matter controls the enrichment of Fe in forming sea ice.. Specifically, we come to the conclusion that the incorporation of DFe is favored by the presence of organic ligands in the source solution.

Effects of UV treatment on orthodontic microimplant surface after autoclaving

이 연구의 목적은, 마이크로임플란트의 보관기간과 증기고압멸균이 표면의 탄소함량에 미치는 영향과, 자외선 처리를 통해 탄소함량을 감소시킬 수 있는가를 조사하는 것이다. 보관기간의 영향을 조사하기 위해, 11년 동안 4개의 다른 시점에서 제작된 4개의 마이크로임플란트 그룹을 비교 실험하였고, 증기고압멸균과 자외선 처치의 효과를 평가하기 위해서는 2개 그룹 (새로 제작된 마이크로임플란트와 제조 후 11년 경과된 마이크로임플란트)을 사용하여 실험하였다. 물 접촉각 실험, 세포활성 검사를 사용하여 표면 탄소함량이 마이크로임플란트의 생물학적 특성에 미치는 영향도 함께 조사하였다. 실험결과, 11년의 보관기간 동안 마이크로임플란트 표면의 탄소함량은 점차 증가함을, 또한 증기고압멸균에 의해서 탄소함량이 증가됨을, 그리고 자외선 처리를 통해서 탄소함량을 유의하게 감소시킬 수 있음을 관찰하였다. 한편, 마이크로임플란트 표면의 탄소함량 감소에 따라 세포활성에는 주목할 변화가 없었으나 표면의 초친수성이 증가됨을 관찰하였다. 이 결과로부터, 마이크로임플란트의 긴 보관기간과 증기고압멸균처리는 표면의 탄소함량을 증가시키지만 자외선 처리는 마이크로임플란트 표면의 탄소함량을 감소시키고 초친수성을 증가시키므로 마이크로임플란트의 안정성 향상을 유도할 수 있을 것이라는 결론을 얻었다.

The Effect of UV Treatment on the Osteoconductive Capacity of Zirconia-Based Materials.

Objective: Improvements in the bioactivity of zirconia implants for accelerated healing and reduced morbidity have been of continuing interest in the fields of dentistry and orthopedic surgery. The aim of the present study was to examine whether UV treatment increases the osteoconductivity of zirconia-based materials. Materials and Methods: Smooth and rough zirconia-based disks and cylindrical implants were treated with UV light for 15 min and subsequently placed in rat femurs. Surface characterization was performed using scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and contact angle measurements. Results: In vivo histomorphometry revealed that the percentage of bone-implant contact and the amount of bone volume, formed around UV-treated implants, increased by 3–7-fold for smooth surfaces and by 1.4–1.7-fold for rough surfaces compared to non-treated specimens at Weeks 2 and 4 of healing, respectively. A biomechanical test showed that UV treatment accelerated the establishment of bone-zirconia integration and enhanced the strength of the bone-implant interface by two-fold. Additionally, surface characterization of the zirconia disks revealed that UV treatment decreased the amount of surface carbon and converted the hydrophilic status from hydrophobic to superhydrophilic. Conclusions: This study indicates that UV light pretreatment enhances the osteoconductive capacity of zirconia-based materials.

상온에서 UV 활성화된 ZnS 나노와이어의 NO2가스 검출 특성

ZnS nanowires were synthesized in order to investigate <TEX>$NO_2$</TEX> gas sensing properties. They were grown on the sapphire substrate using ZnS powders. SEM (scanning electron microscopy) showed the diameter and length of the ZnS nanowires were approximately in the range of 50 - 100 nm and a few <TEX>$10s\;{\mu}m$</TEX>, respectively. They were also found to be composed of Wurtzite- structured single crystals from TEM (transmission electron microscopy) analysis. <TEX>$NO_2$</TEX> gas sensing performance of the ZnS nanowire was measured with electrical resistance changes caused by <TEX>$NO_2$</TEX> gas with a concentration of 1-5ppm. The sensor was UV treated with an intensity of <TEX>$1.2mW/cm^2$</TEX> to facilitate charge carrier transfer. The responses of the ZnS nanowires to the <TEX>$NO_2$</TEX> gas at room temperature, treated with UV of two different wavelengths of 365 nm and 254 nm, are measured to be 124.53 - 206.87 % and 233.97 - 554.83%, respectively. In the current work, the effect of UV treatment on the gas sensing performance of the ZnS nanowires was studied. And the underlying mechanism for the electrical resistance changes of the ZnS nanowires by <TEX>$NO_2$</TEX> gas was also discussed.

Cinnamoyl Alginate Microspheres: Effect of UV-Treatment on Release of FITC-Dextran

Cinnamoyl alginate microspheres were prepared using the water droplets of W/O emulsions as a template. Cinnamoyl alginates having variable content of the cinnamoyl group were prepared by a condensation reaction. The photo-dimerization degree of the cinnamoyl group increased as the molar ratio of pyranose unit/cinnamoyl group increased from 1:0.043 to 1:0.18. The air/water interfacial activity of cinnamoyl alginate also increased with increasing the molar ratio. Aqueous solution of cinnamoyl alginate was dispersed in mineral oil to obtain W/O emulsion. UV light (254 nm, 6 W) was irradiated to the emulsion to dimerize the cinnamoyl groups, and CaCl2 was added to the emulsion to cross-link the cinnamoyl alginate. The surface of UV-treated microspheres was rougher than that of UV-untreated microspheres, possibly due to the photo-dimerization-induced tension on the alginate chains. The release degrees for 24 hours of fluorescein isothiocyanate-dextran (FITC-dextran; MW 4000) from UV-treated microspheres were markedly higher than those from UV-untreated ones. This is possibly due to the intramolecular dimerization of cinnamoyl group. The UV irradiation-induced percentage increase in the maximum release degree was greater as the content of cinnamoyl group was higher.

Effect of UV Treatment on Optical Properties of Low-Density Polyethylene Films Doped with Eu(TTA)&lt;sub&gt;3&lt;/sub&gt;phen Complex

Low-Density Polyethylene (LDPE) films doped with Eu (TTA)3phen complex (TTA=2-thenoyltrifluoroacetone, phen=1,10-phenanthroline) were fabricated by hot-blowing technique for thickness of 100 μm. The films were doped with 0.1 % of Eu (TTA)3phen to the total weight of LDPE and exposed to UV irradiation from deuterium lamp for 5, 10, 20, 40 and 60 hours to investigate the effect of its optical properties. The films were characterized by Spectrofluorometer, UV/VIS Spectrophotometer and FT-IR Spectrometer to measure their emission spectra, lifetimes, transmission transparency and chemical bonding. Photoluminescence of the room-temperature Eu (TTA)3phen doped films consist of typical Eu3+emission transition lines with hypersensitive5D07F2emission band at 610 nm. After 20 hours UV treatment, the peak intensity dropped by 90 % and shortened the luminescent lifetimes from 0.654 ms to 0.305 ms. Longer UV treatment also has accelerated degradation in doped LDPE films shown by significant reducing in absorption peak of FTIR at 3395, 3186 and 1645 cm-1. The results would provide a mechanism to improve the lifetime of the LDPE by utilizing the light-manipulation property of Eu (TTA)3phen complex to absorb UV spectrum and covert into red emission.Keywords: LDPE, rare-earth complex, photoluminescence

Modification of Post-Etch Residues by UV for Wet Removal

In back-end of line processing, the polymer deposited on the dielectric sidewalls during the etch must be removed prior to subsequent processing steps to achieve high adhesion and good coverage of materials deposited in the etched features [1,. Typically, this is done by a combination of short plasma treatment and diluted wet clean, or by wet cleans alone. On the one hand, for porous dielectric stacks, a mild plasma treatment that preserves the integrity of the low-k dielectrics would not be sufficient to efficiently remove this residue. Furthermore, aqueous cleaning solutions is not efficient to achieve a complete removal without etching the underlying layer. Hence appropriate wet clean chemistries are needed to dissolve/decompose these polymers without etching the dielectric. On the other hand, analytical techniques available for direct characterization of sidewall polymer are limited. For a fast screening of potential chemistries capable of dissolving/removing polymer residues generated during the low-k etch, a fluoropolymer deposited on a blanket, checkerboard low-k substrate was used as a model polymer. In our recent study [, using X-ray photoelectron spectroscopy (XPS), it was shown that the polymer was composed of CF, CF2, and CF3 groups. This model polymer was found to be very similar to the polymer residue generated during the etch of the low-k stack using similar plasma. The present study mainly focused on the effect of UV treatment and the concentration of active component in wet clean solution on the structure change of the polymer and the enhancement of polymer removal.

Effect of UV-Treatment on Properties of Biodegradable Film From Rice Starch

Effect of UV-Treatment on Properties of Biodegradable Film From Rice Starch

The Effects of UV Exposure on Plasma-Enhanced Atomic Layer Deposition ZnO Thin Film Transistor

We investigated the effects of UV treatment on the device properties of a plasma-enhanced atomic layer deposition (PE-ALD) ZnO thin film transistor (TFT). Remote PE-ALD ZnO thin films were used as active layers for bottom-gate TFT devices. The as-deposited PE-ALD ZnO film at a growth temperature of 200°C has an overly small carrier concentration, which produces a TFT device with no modulation by gate voltage sweep. However, after UV light exposure, the device shows proper TFT modulation by gate voltage. The threshold voltage (V th ) of the device can be controlled to the negative direction by increasing the UV exposure time. V th moves from 17.8 to -6.5 V with an increase in UV exposure time from 3 to 120 min.

Effect of UV treatment on antioxidant capacity, antioxidant enzyme activity and decay in strawberry fruit

The changes in antioxidant capacity, enzyme activity and decay development in strawberry fruit ( Fragaria x ananassa Duch.) illuminated with different UV-C dosages were investigated. Three UV-C illumination durations and dosages, 1, 5 and 10 min, (0.43, 2.15 and 4.30 kJ m −2) tested promoted the antioxidant capacity and enzyme activities and significantly reduced the severity of decay during storage at 10 °C compared to the control. UV-C illumination for 5 and 10 min showed the best results for enhancing antioxidant capacity expressed as oxygen radical absorbance capacity (ORAC) values after storage for 15 days among all the treatments. These treatments also enhanced the activities of antioxidant enzymes including glutathione peroxidase (GSH-POD), glutathione reductase (GR), superoxide dismutase (SOD), ascorbate peroxidase (AsA-POD), guaiacol peroxidase (G-POD), monodehydroascorbate reductase (MDAR), and dehydroascorbate reductase (DHAR). The nonenzyme components such as reduced glutathione (GSH) and oxidized glutathione (GSSG) also were increased by UV-C exposure. All UV-C dosages increased the phenolic content of strawberry fruits as well. Total anthocyanin content increased during storage in all treatments. However, UV-C illumination showed little effect on the anthocyanin accumulation. All UV-C dosages retarded the development of decay comparing to control treatment, but 5 and 10 min UV-C illumination gave the best decay inhibition.

Influence of UV Exposure on Phenolic Acid Content, Mechanical Properties of Bran, and Milling Behavior of Durum Wheat (Triticum Durum Desf.)

ABSTRACTDurum wheat bran was exposed to UV radiation up to 48 hr and the changes in ferulic acid (FA) content in the peripheral part s of grain were measured. The treatment resulted in a 25% decrease in FA monomer and a 44% decrease in dehydrodiferulic acid (DHD) ester‐linked to the cell‐wall arabinoxylans. This reduction was partly explained by a significant increase of FA (30%) and DHD (36%) engaged in hot alkali‐labile linkages. The results suggest that UV irradiation induced the formation of new cross‐links between feruloylated arabinoxylan and lignin in the pericarp. The effects of UV treatment on bran mechanical properties and wheat milling behavior were investigated. UV irradiation for 15 hr increased the stress to rupture by 30% and decreased the extensibility of bran tissues by 54%. This stiffening was associated with an increase in bran friability during grinding. Although this effect was due in part to the hydrothermal history of the grain, chemical modification induced by UV significantly influenced the size reduction of bran particles, which can be explained by the modification of the mechanical properties of bran. Relationships between the organization of cell‐wall polymers, the mechanical properties of tissues, and the behavior of wheat grain during milling were investigated.

Effects of elevated ultraviolet radiation and endophytic fungi on plant growth and insect feeding in Lolium perenne, Festuca rubra, F. arundinacea and F. pratensis

Plants of perennial ryegrass ( Lolium perenne L.), red fescue ( Festuca rubra L.), tall fescue ( F. arundinacea Schreb.) and meadow fescue ( F. pratensis Huds) were exposed at an outdoor facility located in Edinburgh, UK to modulated levels of UV-B radiation (280–315 nm) using banks of cellulose diacetate filtered UV-B fluorescent lamps that also produce UV-A radiation (315–400 nm). The plants were derived from a single clone of each species and were grown both with and without colonization by naturally-occurring fungal endophytes. The UV-B treatment was a 30% elevation above the ambient erythemally-weighted level of UV-B during July to October. Growth of treated plants was compared with plants grown under elevated UV-A radiation alone produced by banks of polyester filtered lamps and with plants grown at ambient levels of solar radiation under banks of unenergized lamps. At the end of the treatment period, sample leaves were collected for feeding trials with the desert locust Schistocerca gregaria (Forsk). The UV-B treatment produced no effects on the aboveground biomass of any of the four grasses. The UV-B treatment and the UV-A control exposure both increased plant height and the number of daughter plants formed by rhizome growth in F. rubra. There were significant effects of endophyte presence on the total fresh and dry weights of F. arundinacea and F. rubra, on fresh weight only in F. pratensis, and on the fresh and dry weights of inflorescence in F. arundinacea and L. perenne. There were no effects of UV treatments on the absolute amounts of leaf consumed or on the feeding preferences of locusts for leaves with or without endophyte in three species: F. rubra, F. arundinacea and L. perenne. In F. pratensis there was no effect of UV treatment on the weight of leaves consumed but a significant UV×endophyte interaction caused by a marked change in feeding preference between leaves with and without endophyte that differed between the UV-B treatment and UV-A control exposures. The alkaloid compounds known as lolines were analysed in leaves of F. pratensis and were only found in plants grown with endophyte. However, there was no significant relationship between total loline content and insect feeding preference. These effects illustrate the potential complexities of species interactions under increasing levels of UV-B. The experiment also demonstrates the importance of appropriate controls in UV lamp supplementation experiments for interpretation of both plant growth and insect feeding effects.

The effect of ultraviolet radiation on early stages of activation of human lymphocytes: inhibition is independent of effects on DNA.

Low doses (30-84 ergs/mm2, 1 erg = 10(7) J) of ultraviolet radiation (UV) caused severe inhibition of the proliferation of human lymphocytes in vitro. Greatest inhibition was produced when resting cells were irradiated immediately prior to stimulation with concanavalin A (Con A); this was true whether activation was measured by the incorporation of labelled leucine, uridine, or thymidine. If UV was applied at 44 h after culture in presence of Con A, the incorporation of [3H]thymidine measured 4 h later was seen to be inhibited but transcription and translation were scarcely affected. UV, applied after the appearance of the Con A induced thymidine transport system, did not inhibit its function. The disaggregation of chromatin and increase in nuclear volume characteristic of, and essential to, the proliferative response of lymphocytes were completely inhibited if the cells were irradiated before mitogen was added to the cultures, but were unaffected if irradiation occurred after 16 h of culture in presence of Con A. Cells irradiated with 84 ergs/mm2 at the onset of culture with mitogen did not show the early increase of cation pump function which is a characteristic of stimulated lymphocytes, when this was measured by means of 86Rb uptake after 2-4 h culture. The mitogen-stimulated activation of cation pump function has previously been shown to be unaffected by concentrations of cycloheximide and actinomycin D which produce virtually complete inhibition of protein and RNA synthesis, respectively. The major inhibitory effect of UV treatment of lymphocytes at onset of culture with Con A is therefore not on DNA or on DNA synthesis, but on some component(s) of the early activation process, possibly at the cell periphery; inactivation of this component prevents cells from proceeding into later stages of the proliferative pathway.